1. Field of Invention
The present invention is directed to high speed data communications cables and transmission media used therein.
2. Discussion of Related Art
Telecommunication cable designs vary according to the role which the cables are meant to fulfill. In building design, it is always of paramount importance to take every precaution possible to resist the spread of flame and the generation of and spread of smoke throughout a building in case of an outbreak of fire. This clearly is a main aim as protection against loss of life and also to minimize the cost of the fire in relation to the destruction of electrical and other equipment. With this in mind, for cables designed for installation in plenum chambers of air circulation systems in buildings, care needs to be taken to ensure that the cables have maximum resistance to flame spread and also produce minimum amounts of smoke which reduces the chances of visibility becoming obscured, thereby greatly increasing the chances of people within the building finding their way to safety.
Conventional designs of data grade telecommunications cables for installation in plenum chambers have a low smoke generating jacket material, e.g. of a PVC formulation or a fluoropolymer material, surrounding a core of twisted conductor pairs, each conductor individually insulated with a fluorinated ethylene propylene insulation layer. The latter is a common choice for conductor insulation in this type of cable, due to its flame retardant, smoke retardant and good electrical properties and which is capable of satisfying recognized plenum test requirements such as the “peak smoke” and “average smoke” requirements of the UL910 Steiner test and/or CSA FT6 (plenum flame test) while enabling the cable to achieve a desired electrical performance under recognized test requirements EIA/TIA-568 and TSB-36 for high frequency signal transmission.